1. Field of the Invention:
This invention relates to a panic-type exit device of the type having a waist-level housing with a vertical rod extending to an upper latch at the top of the door. More specifically, the invention contemplates a provision in such a push rod of a fusible section which will melt and preclude the unintentional opening of the door as the push rod expands in a fire.
2. Description of the Prior Art:
In the prior art, of course, it is common to provide exit doors in public buildings with panic-type operators. Some of these operators include latches at the top of the door which are operated by a push rod extending up from a housing adjacent the door operator. The upper latch is arranged so that a vertically upward movement of the push rod will disengage the latch from its strike in the upper member of the door frame.
A problem is presented by the arrangement described in that in the event of a hot fire where it is desired to have the doors completely closed to avoid spreading to adjacent structures, the heat of the fire can effect an elongation of the push rod to cause an inadvertent unlatching of the door. The pressure built up inside the fire area, or the pressure of the water from a fire hose, can thereafter in effect "blow" the door open to break down the isolation of the fire area and threaten further spread.
In the prior art, there are teachings of the idea of fusible portions of latch structure to avoid the unlatching of the door on occasion of fire. An example is disclosed in the Dusing U.S. Pat. No. 2,772,905, issued Dec. 4, 1956. In this patent, structure surrounding the latch operator, being of a special low temperature alloy, melts away in the event of a fire to preclude the warpage of a door causing the door to become unlatched.